Tube coating film and apparatus

ABSTRACT

This invention relates to an apparatus for coating the inside of tubular film manufactured by a blown film process. The coating apparatus includes a dispensing means comprising a coating conduit passing through a tubular film die into a pressurized area of the said film with a distributing means connected to the coating conduit, said distributing means include a vaporizing means having temperature control means.

United States Patent 1191 Stannard 1 51 Jan. 9, 1973 s41 TUBE COATING FILM AND 2,533,330 1/1952 ECkCl'l ..264/209 APPARATUS 3,068,516 12 1962 HOfBl 2,979,777 4 1961 0 1d [76] invent: sia'mardi 43 3,560,602 2/1971 114212111161... ..264/173 Court, Oakland Park, 1,730,638 10/1929 Young ..18/14 11 3,183,288 5/1965 "ra 16r 61 a1. ..18/14 11 [22] 1970 1,196,648 8/1916 1316661631 ..18/14 11 [21] Appl. N0.: 94,355 3,090,998 5/1963 l-leisterkamp et a1. ..264/95 Related U.S. Application Data Continuation-impart of Ser. No. 14,403, Feb. 26, 1970, abandoned.

U.S. Cl. ..425/72, 118/5, 118/48, 264/83, 264/95, 264/173, 425/106, 425/326 Int. Cl ..B05c 7/00, B29c 17/07, 829d 7/20 Field of Search ..264/95, 171, 173, 209,210, 264/82, 83, 129, 131; 425/72, 326,131,133, 94, 97, 95, 96, 106; 118/48, 5; 117/95 References Cited UNITED STATES PATENTS 12/1964 Berggren et a1. ..264/209 Primary ExaminerRobert F. White Assistant Examiner leffery R. Thurlow Attorney-Eugene F. Malin [57] ABSTRACT This invention relates to an apparatus for coating the inside of tubular film manufactured by a blown film process. The coating apparatus includes a dispensing means comprising a coating conduit passing through a tubular film die into a pressurized area of the said film with a distributing means connected to the coating conduit, said distributing means include a vaporizing means having temperature control means.

1 Claim, 6 Drawing Figures Pmmninm 9191s 3.709.642

SHEET 2 OF 2 FIG.5

' mvmnk. FORREST B. STANNARD TUBE COATING FILM AND APPARATUS This is a continuation-in-part patent application of Forrest B. Stannard, Ser. No. 14,403, filed Feb. 26, 1970, entitled Tube Coating Film and Apparatus, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a new and improved apparatus for coating the inside of tubular film during the blown film manufacturing process.

In the past, tubular film has been coated by applying the coating to the outside surface of the film as the of was moved past a wiper mechanism. Also various coating methods have been used to coat the blown film after it has been slit and rolled into a flat sheet.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to an apparatus for coating the inside of tubular film during the blown film manufacturing process. The apparatus includes a conduit passing from a pressurized source of the coating material through the die core inside of the extruder. A valve may be used to control the quantity of coating material passing through the die core onto the film. A dispensing head is connected to the distal inside end of the conduit. The liquid dispensing head may include means for spraying the liquid, means leading to a pool of liquid in the tube, or means for vaporizing the coating liquid within the blown tube and for condensing the vaporized material. When a gas is dispensed into the tube means for condensing, the gaseous material is used to coat the tube. When powder is dispensed, the head may include a nozzle for spraying the powder onto the inside of the blown tube. The methods provide means for coating the inside surface of the tube with a uniform layer of coating material. The coating material may be solidified from a liquid by cooling means along the outside of the blown tube.

It is an object of this invention to provide a non-complex coating apparatus for coating the inside surface of the blown film during the extrusion process.

It is another object of this invention to provide a new and improved apparatus for manufacturing blown film with a uniform coating thickness on the inside surface of the film.

A further object of this invention is to provide a low cost apparatus for producing coated blown film.

In accordance with these and other objects which will be apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side view of the blown film extrusion apparatus showing the coating conduit;

FIG. 2 is a front view tilted forward partially in cross section of a liquid vaporizing apparatus showing the top surfaces;

FIG. 3 is a front view tilted forward of the powder dispensing head;

FIG. 4 is a side view, partially broken away and partially in cross section, of the blown film with a liquid pool for coating the film;

FIG. 5 is a cross section of the first set of rollers in FIG. 4; and

FIG. 6 is a front view of a ring sprayer and cooling coils.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawing, especially to FIG. 1, showing the new and improved apparatus for coating the inside of tubular film during a blown tube extrusion process, the extruder system, generally designated by numeral 2, includes a hopper 4, extruder cylinder, heaters 6, die 8, and various blown tube handling means. The raw material used to manufacture the film is fed into the upper opening in the hopper 4. The material is fed by gravity from the hopper 4 into the extruder. The extruder screw forces the raw material through a heated section of the extruder cylinder which includes heaters. as illustrated by numeral 6, The raw material is forced through the extruder cylinder and out through die 8 in the form of tube 10. When the open end of the tube is closed by pinch roller and air is forced into the tube, an air bubble is trapped in the tube 10. The air pressure, the size of the die openings, the temperature of the raw material, and the speed in which the tube is drawn away from the die controls the wall thickness of the blown tube, as is well known in the art. The air pressure in the blown tube is controlled by valve 40 in the air conduit 12.

The pressurized air is fed into the blown tube 10 through the air conduit 12. The coating material is fed into the blown tube through pipe 14 that passes through conduit 12. The pressurized air and coating material are dispensed into the blown tube through various dispensing means.

The extruded tube is manufactured in the ordinary manner. As the molten plastic moves upward from the mouth of the die, the diameter of the tube expands until it reaches the frost line 18. The molted material solidifies at the frost line 18. The pinch rolls 20 and 22 flatten the blown tubes. That it may be rolled for storage. The pinch rolls also hold the air bubble in the blown tube. Alignment rolls 24 and 26 guide the blown tube, in the area of numeral 28, into the pinch rolls 20 and 22. The flattened tube is drawn onto storage roll 32. The rolls are driven by a drive means, not shown.

Referring now to FIG. 2, the distal end of the coating pipe 14 projects outward from the distal end of air pressure pipe 12. The air and coating material conduits l2 and 14 respectively enter the blown tube through the die core 34. The die 8 includes a die core 34, a die opening or mouth 36, and outer die portion 38, When a liquid is to be vaporized in the blown tube the liquid distributing means includes a cup 48 and heater element 52 at the distal end of the pipe 14 adjacent opening 42. The flow of liquid into the cup 48 is controlled by valve 46. The liquid flows out of opening 42 into the heated cup 48. It should be noted that the liquid may be poured on the hot die to evaporate the liquid. In FIG. 2, the liquid is heated by heating element 52 connected to the bottom of the cup 48. The heating element 52 may be an electrical heater connected to a control means and a power source, not shown, to control the amount of coating material vaporized in the blown tube. The heating element control means may include temperature control means, not shown. As the vapor rises, the inner wall of the blown tube is coated with the coating material. Cooling coils as shown in FIG. 6 may be used to condense the coating material onto the inside surface of the blown tube. The coating may be left in a liquid state on the inside surface of the blown tube or the coating may be solidified by cooling the liquid material on the inside surface of the tube below the liquids freezing point in order to provide a solid coating in the tube.

It should be noted that the coating material may be applied by using a pool of liquid as shown in FIG. 4. The pool of liquid is formed after the pinch rollers 70 and 72, and before the rollers 82 and 84. The rollers 70 and 72 include notches 74 and 76 about the circumference of each roller as shown in FIG. 5. The notches 74 and 76 allow the pipe extension 78 to pass though the pinch rollers to deliver the liquid into pool 80. The pinch rollers 70 and 72 maintain the pressure in tube 10. The pool of liquid 80 coats the inside surfaces of the tube. The pinch rollers 82 and 84 contain the fluid in the pool. Cooling coils may be located beyond the pinch rollers 82 and 84 to solidify the liquid on the film.

The liquid coating material may be sprayed on the inside of the blown tube by using the circular sprayer 60, shown in FIG. 6. The sprayer 60 is a ring sprayer having a plurality of nozzles 62 spaced at intervals along the outside of the tubular ring. The sprayer may be held in the blown tube by a connecting pipe extension 64 con nected to the opening 42 in pipe 14. The liquid may be solidified by placing cooling coils 66 adjacent the outside of the tube abovethe sprayer 60. The cooling coils are connected to a refrigerating source, not shown, by connecting pipe 68.

When the coating material is gas it may be dispensed into the tube and allowed to condense on the sides of the tube. Cooling coils may be used to aid in condensing the gas in the tube.

Referring now to FIG. 3 showing a powder distribution means 56 connected to the distal end of coating pipe 54. The valve 46 controls the quantity of powder being forced into the blown tube through head 56. The powder may be blown onto the inner surface of the blown tube through nozzle 56 or may be blown into the air bubble in order that it may be attracted by static electricity onto the sides of the tube. The powder may also be blown into the blown tube and allowed to rise with the moving tube-in order that the powder may be trapped by the pinch rollers 20 and 22. The powdery material may be blown onto the tube below the freeze line in order to melt the powder to form a layer of coating material on the inside surface of tube. The melted powder will combine with the plastic film, both of which solidify at the freeze line.

If the tube is extruded downwardly, not shown, a reservoir of liquid may be trapped above the pinch rollers. This would be similar to the liquid held between rollers and 72 and rollers 82 and 84.

The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom with-in the scope of the invention and that obvious modifications will occur to a person skilled in that art.

What is claimed is:

l. A coating apparatus for coating the inside surface of a blown tube between the die and the pinch rollers, com rising:

a ie for forming a tube, a pressure means including a pressure conduit passing through the die to pressurize the tube formed by the die,

a pair of pinch rollers spaced from said die to form a pressure barrier at the opposite end of the tube formed by the die,

dispensing means including a coating conduit passing through the die into the pressurized area of the tube to transport coating material through the die, the conduit projects outward from the face of the die, the dispensing means includes a distributing means connected to the outward end of the coat ing conduit, said distribution means includes a vaporizing means to hold a quantity of the coating material within the pressurized tube, and the vaporizing means includes a material temperature control means for changing the temperature of the coating material to vaporize the coating material within the pressurized tube. 

1. A coating apparatus for coating the inside surface of a blown tube between the die and the pinch rollers, comprising: a die for forming a tube, a pressure means including a pressure conduit passing through the die to pressurize the tube formed by the die, a pair of pinch rollers spaced from said die to form a pressure barrier at the opposite end of the tube formed by the die, dispensing means including a coating conduit passing through the die into the pressurized area of the tube to transport coating material through the die, the conduit projects outward from the face of the die, the dispensing means includes a distributing means connected to the outward end of the coating conduit, said distribution means includes a vaporizing means to hold a quantity of the coating material within the pressurized tube, and the vaporizing means includes a material temperature control means for changing the temperature of the coating material to vaporize the coating material within the pressurized tube. 